1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same.
2. Description of the Related Art
Chip size packages (CSPs) are generally completed directly after each of semiconductor-processed wafers is singulated into a semiconductor chip. However, wafer level packages (WLPs) are completed after circuit is redistributed or is flip-chip bumped in a wafer state and then is singulated. Therefore, wafer level chip size packages (WLCSPs) are processed in a wafer level and have the same size as the semiconductor chip.
WLCSPs are processed in a wafer level and have the same size as the semiconductor chip. The size of packages is the same as that of chips. Thus, WLCSPs have almost the same size as that of semiconductor chips and are small-sized. WLCSPs are processed in a wafer level, making it possible to mass-produce WLCSPs, thereby reducing their manufacturing costs.
WLCSPs comprise wafers, redistribution layers formed on the upper surfaces, and solderballs. Semiconductor chips having bond pads are formed on the upper surface of wafers, and redistribution layers are formed on the upper surfaces of wafers in order to redistribute bond pads. In more detail, redistribution layers are used to redistribute peripherally formed bond pads in a grid pattern. Further, redistribution layers are generally formed of copper (Cu) having excellent electrical characteristics.
However, since copper (Cu) easily responds to oxygen in the atmosphere as is widely well known, its surface is easily oxidized during a high temperature hardening process, etc. Therefore, such property of copper (Cu) acts as a factor of dropping a contact power between redistribution layers and solder balls.
Meanwhile, WLCSPs that are realized as final package products perform a drop test to check reliabilities of electric characteristics and hardness. However, conventional WLCSPs comprise solder balls formed on just right surfaces of wafers so that mechanical stress transferred from outside is delivered to solder balls, which drops a board level reliability including solder bonding.
At the same time, external mechanical stress is also delivered to redistribution layers. In this regard, since redistribution layers have a monotonous structure using plated copper (Cu), they cannot absorb external shocks, which causes a crack at an edge of surfaces where solder balls and redistribution layers contact.